Slim led package

ABSTRACT

Disclosed herein is a slim LED package. The slim LED package includes first and second lead frames separated from each other, a chip mounting recess formed on one upper surface region of the first lead frame by reducing a thickness of the one upper surface region below other upper surface regions of the first lead frame, an LED chip mounted on a bottom surface of the chip mounting recess and connected with the second lead frame via a bonding wire, and a transparent encapsulation material protecting the LED chip while supporting the first and second lead frames.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the National Stage of International Application No.PCT/KR2008/006777, filed Nov. 18, 2008, and claims priority from and thebenefit of Korean Patent Application No. 10-2007-0124469, filed on Dec.3, 2007, which are both hereby incorporated by reference for allpurposes as if fully set forth herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a light emitting diode (LED) packageand, more particularly, to a slim LED package that is significantlyreduced in thickness without substantially reducing luminescenceefficiency or while improving the luminescence efficiency.

2. Discussion of the Background

An LED emits light through recombination of electrons and holes byapplication of an electric current. An LED package means a packagestructure in which a light emitting diode chip, that is, an LED chip, isreceived. Many kinds of LED packages, particularly, a lead frame typeLED package and a printed circuit board (PCB) type LED package, are wellknown in the art. The lead frame type LED package has a structurewherein a cavity of a housing for supporting a lead frame is filled withan encapsulation material, with the LED chip positioned in the cavity ofthe housing. The PCB type LED package has a structure wherein the LEDchip is directly mounted on a PCB and covered with the encapsulationmaterial.

For the lead frame type LED package, the housing supporting the leadframe has an excessive thickness, which makes it difficult to fabricatea thin lead frame type LED package. On the other hand, since the PCBtype LED package does not include a housing, it can be more easilyfabricated to have a thin structure than the lead frame type LEDpackage.

However, there are many restrictions in thickness reduction of the PCBtype LED package. In other words, since the thickness of the PCB typeLED package is determined by thicknesses of the PCB and LED chips, and aloop height of a bonding wire even without considering the encapsulationmaterial, it is difficult to achieve an overall thickness reduction andslimness of the PCB type LED package.

Further, the encapsulation material of the LED package, which covers theLED chip, undergoes a yellowing phenomenon by energy generated from theLED chip emitting light. Such a yellowing phenomenon is a main cause ofdecreased luminescence performance and lifetime of the LED package. Toovercome such problems, new LED packages have been developed to have aheat sink structure. In detail, the lead frame type LED package furtherincludes a heat dissipation slug inserted into the housing by molding.Such a structure of the lead frame type LED package requires addition ofcomponents and a complicated manufacturing process, thereby decreasingeconomic feasibility. For the PCB type LED package, B-T resin on whichthe LED chip is mounted has a low heat dissipation performance, and itis difficult to have the heat sink structure.

SUMMARY OF THE INVENTION

Therefore, an aspect of the present invention is to provide a slim LEDpackage that is configured to allow a transparent encapsulation materialto directly support a lead frame without a housing, that has a reducedoverall thickness by reducing the thickness of a chip mounting region ofthe lead frame, and that exhibits good heat dissipation performance.

In accordance with an aspect of the present invention, a slim LEDpackage includes: first and second lead frames separated from eachother; a chip mounting recess formed on one upper surface region of thefirst lead frame by reducing a thickness of the one upper surface regionbelow other upper surface regions of the first lead frame; an LED chipmounted on a bottom surface of the chip mounting recess and connectedwith the second lead frame via a bonding wire; and a transparentencapsulation material protecting the LED chip while supporting thefirst and second lead frames. The LED chip may have a thickness lowerthan or equal to a depth of the chip mounting recess.

The chip mounting recess may be formed by thickness-etching the oneupper surface region of the first lead frame. Herein, the term“thickness-etching” refers to etching performed to reduce the thicknessof a material, that is, the thickness of the one upper surface region ofthe lead frame.

The slim LED package may further include a bonding recess formed on oneupper surface region of the second lead frame by reducing a thickness ofthe one upper surface region of the second lead frame below other uppersurface regions of the second lead frame, one end of the bonding wirebeing bonded into the bonding recess. The bonding recess may be formedby thickness-etching the one upper surface region of the second leadframe.

The slim LED package may further include openings or grooves formed onan upper or lower surface of the first or second lead frame to increasea bonding force between the first and second lead frames and theencapsulation material. Alternatively, the slim LED package may furtherinclude scratches formed on an upper or lower surface of the first orsecond lead frame to increase the bonding force between the first andsecond lead frames and the encapsulation material. Further, the LED chipmay have a lower height than the depth of the chip mounting recess. Thefirst and second lead frames may have opposite sides facing each otherand including linear or rounded slant parts facing each other in aslanted state. At least one of the opposite sides may have a depressedpart formed thereon to widen a separation between the first lead frameand the second lead frame.

The slim LED package may further include a phosphor in the encapsulationmaterial. The slim LED package may further include an adjacent resinpart formed in the chip mounting recess inside the encapsulationmaterial, and the phosphor may be disposed in the adjacent resin part.Alternatively, the phosphor may be disposed in a resin constituting theencapsulation material or may be coated on the LED chip by conformalcoating.

The encapsulation material may be formed by transfer molding with asolid resin, particularly, a solid EMC. Alternatively, the encapsulationmaterial may be formed by injection molding with a liquid resin.

According to one embodiment of the present invention, the LED package isconfigured to mount an LED chip on a chip mounting recess, which isformed on a predetermined region of a lead frame by reducing thethickness of the predetermined region, such that the thickness of theLED chip partially overlaps the thickness of the lead frame, whereby theLED package can be significantly reduced in overall thickness, achievingan ultrathin slimness. Further, the lead frame on which the LED chip ismounted and the lead frame with which a bonding wire is connected have asignificantly increased area exposed to the bottom, so that the LEDpackage has greatly improved thermal dissipation efficiency.Additionally, a bonding recess is formed on the lead frame by reducingthe thickness of a part of the lead frame with which the bonding wire isconnected, and is provided therein with a wire ball to be connected withthe bonding wire. As a result, a factor causing an increase in thicknessof the LED package can be eliminated, so that the LED package is furtherslimmed. Further, according to one embodiment of the present invention,openings or grooves are formed on the lead frames to increase a bondingforce between the lead frames and an encapsulation material, therebypreventing separation of an interfacial surface between theencapsulation material and the lead frames. Moreover, an inside surfaceof the chip mounting recess serves to improve luminescence efficiency,as compared to a conventional PCB type LED package that is configured toreflect light emitted from the LED chip to an upper side.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and advantages of the presentinvention will be more clearly understood from the following detaileddescription taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 is a plan view of a slim LED package according to one embodimentof the present invention;

FIG. 2 is a cross-sectional view taken along line I-I of FIG. 1;

FIGS. 3 to 5 are cross-sectional views of slim LED packages according tovarious embodiments of the present invention;

FIG. 6 is a cross-sectional view of a slim LED package according to yetanother embodiment of the present invention; and

FIG. 7 is a cross-sectional view taken along line II-II of FIG. 6; and

FIGS. 8( a) and 8(b) are cross-sectional views of a slim LED packageaccording to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Exemplary embodiments of the present invention will be described indetail with reference to the accompanying drawings. The embodiments aregiven by way of illustration for complete understanding of the presentinvention by those skilled in the art. Hence, the present invention isnot limited to these embodiments and can be realized in various forms.Further, for convenience of description, width, length, and thickness ofcomponents are not drawn to scale in the drawings. Like components areindicated by like reference numerals throughout the specification.

FIG. 1 is a plan view of a slim LED package 1 according to oneembodiment of the invention, and FIG. 2 is a cross-sectional view takenline I-I of FIG. 1.

Referring to FIGS. 1 and 2, a slim LED package 1 of this embodimentincludes first and second lead frames 12, 14 separated from each other.The first lead frame 12 has an LED chip 2 mounted thereon, and thesecond lead frame 14 is electrically connected with the LED chip 2 via abonding wire W. The bonding wire W is connected with the second leadframe 14 via a wire ball or soldering ball (not shown).

The first and second lead frames 12, 14 are supported by a transparentencapsulation material 20. The transparent encapsulation material 20 isformed to entirely cover and protect the LED chip 2 and bonding wire Wby molding. The encapsulation material 20 may be formed by transfermolding with an epoxy molding compound that is a solid epoxy resin. Forexample, the transfer molding is performed by compressing epoxy moldingcompound (EMC) powder at a proper pressure into a tablet-shape, followedby positioning and molding the tablet-shaped EMC in a mold at hightemperature and pressure conditions to form the encapsulation material20.

In this embodiment, the encapsulation material 20 is formed by transfermolding, but the present invention is not limited thereto.Alternatively, the encapsulation material 20 can be formed by injectionmolding, in which a liquid resin is injected into a mold. Theencapsulation material 20 may be formed of other kinds of transparentresins such as epoxy-based or silicone-based resins, as well as the EMC.

The first lead frame 12 is formed with a chip mounting recess 121 on itsupper surface, and the chip mounting recess 121 has the LED chip 2mounted on a bottom surface thereof in a die-attachment manner. The chipmounting recess 121 is formed by reducing the thickness of one uppersurface region of the first lead frame 12 below other regions of thefirst lead frame 12, instead of bending the lead frame to form areflection cup as in the prior art. Accordingly, the first lead frame 12has a decreased thickness only in the region of the first lead frame 12where the LED chip 2 is mounted, whereby a mounting height of the LEDchip 2 is lowered to contribute to slimness of the LED package 1 throughan overall thickness reduction of the LED package 1. Further, an insidesurface of the chip mounting groove 121 serves as a reflector forreflecting light, thereby enhancing luminescence efficiency of the LEDpackage 1.

The chip mounting recess 121 may be formed by thickness-etching, whichis performed for the purpose of reducing the thickness of the leadframe. At this time, etching can be performed, with the upper surface ofthe first lead frame 12 except for the chip mounting region covered witha mask. Further, the chip mounting recess 121 may have a thickness ofabout half of the thickness of the first lead frame 12. However, itshould be noted that the present invention is not limited thereto.

Further, the LED chip 2 may have a thickness less than or equal to thedepth of the chip mounting recess 121 to prevent the height of the LEDchip 2 from affecting a thickness increase of the LED package 1. Inother words, it is desirable that the depth of the chip mounting recess121 be set greater than or equal to the height of the LED chip 2.

As clearly shown in FIG. 2, the first and second lead frames 12, 14 arerespectively formed on lower surfaces thereof with grooves 122, 142,which are filled with a portion of the encapsulation material 20 duringthe molding process. As a result, the portion of the encapsulationmaterial 20 engages with the grooves 122, 142, and a contact areabetween the lead frames 12, 14 and the encapsulation material 20increases, thereby increasing a bonding force between the encapsulationmaterial 20 and the lead frames 12, 14. The grooves 122, 142 are alsoformed by reducing the thickness of predetermined regions of the lowersurfaces of the first and second lead frames 12, 14, and preferably bythickness-etching as described above. Alternatively, instead of formingthe openings or grooves, as shown in FIG. 8( a) and FIG. 8( b),scratches 122′ and 142′ may be formed on the upper or lower surfaces ofthe first and second lead frames 12, 14, respectively, to increase thebonding force between the lead frames 12, 14 and the encapsulationmaterial 20.

Referring again to FIG. 2, the encapsulation material 20 contains aphosphor 202 that is excited by light of a predetermined wavelength andemits light of a different wavelength. The phosphor 202 contributes togeneration of white light through wavelength conversion by convertinglight emitted from the LED chip 2. In this embodiment, the phosphor 202is mixed with a resin prepared as a molding material and is disposed inthe encapsulation material 20 by the molding process using the moldingmaterial. For example, when forming the encapsulation material 20 bytransfer molding, a mixture of EMC and the phosphor 202 is prepared andused as the material for the transfer molding.

Next, various other embodiments of the present invention will bedescribed. In description of the embodiments, a repetitious descriptionwill be omitted, and, the same or similar elements will be denoted bythe same reference numerals as those of the above description.

In FIG. 3, a bonding recess 141 is shown, which is formed by reducingthe thickness of one upper surface region of a second lead frame 14below the thickness of other regions thereof. The bonding recess 141 canalso be formed by the thickness-etching as in the formation of the chipmounting recess 121 of the aforementioned embodiment. At this time, oneend of a bonding wire W is connected with the second lead frame 14within the bonding recess 141.

Although not shown in the drawings, a wire ball is located in thebonding recess 141 such that the one end of the bonding wire W isconnected with the wire ball in the bonding recess 141, therebypreventing a thickness increase of the LED package due to the height ofthe wire ball. A size increase of the wire ball ensures that the bondingwire W can be more rigidly secured to the second lead frame 14. Here,the formation of the bonding recess 141 enables more freedom to increasethe size of the wire ball.

Referring to FIG. 4, in another embodiment of the present invention, aresin 21 containing a phosphor 202 is restrictively provided in the chipmounting recess 121 to cover the LED chip 2 in an adjacent distance.Herein, the resin 21 filling in the chip mounting recess 121 will bedefined as an “adjacent resin part.” The adjacent resin part 21 preventsthe phosphor 202 from being scattered within the encapsulation material20, and allows the phosphor 202 to be located around the LED chip 2.This configuration can improve color conversion efficiency by thephosphor 202, and can provide light consisting of uniformly mixed colorswhen viewed outside the LED package 1.

Alternatively, the adjacent resin part 21 may not contain the phosphor202. For example, the encapsulation material such as epoxy is vulnerableto heat, and can cause thermal deformation or a yellowing phenomenonaround the LED chip 2. Here, when the adjacent resin part 21 formed inthe chip mounting recess 121 is made of a silicone resin, which isessentially invulnerable to heat, it is possible to efficiently preventdeterioration in performance or lifetime of the LED package 1 caused bythe yellowing phenomenon. When using the silicone as a material for theadjacent resin part 21 to prevent thermal deformation or the yellowingphenomenon, the phosphor 202 can be included in the adjacent resin part21 or omitted therefrom without any influence on the effect ofpreventing thermal deformation or the yellowing phenomenon.

Alternatively, the phosphor 202 can be coated on the surface of the LEDchip 2 by, for example, conformal coating via electrophoresis. In thiscase, the LED package 1 has a configuration as illustrated in FIG. 5.

FIG. 6 is a cross-sectional view of a slim LED package 1 according toyet another embodiment of the present invention, and FIG. 7 is across-sectional view taken along line II-II of FIG. 6.

Referring to FIGS. 6 and 7, instead of the grooves 122, 142 (see FIG. 2)of the above embodiment, first and second lead frames 12, 14 of thisembodiment are formed with openings 123, 143, which penetrate the firstand second lead frames 12, 14 in the vertical direction, to increase thebonding force between an encapsulation material 20 and the lead frames12, 14. The openings 123, 143 can be formed by pressing or by etchingthe lead frames 12, 14 in the thickness direction.

As clearly shown in FIG. 6, the first and second lead frames 12, 14include first and second slant parts 125, 145, which are formed onopposite sides of the lead frames 12, 14 facing each other in aninclined state. That is, the first slant part 125 is formed on one sideof the first lead frame 12 facing the other side of the second leadframe 14 to be inclined towards right and left sides of the first leadframe 12. Further, the second slant part 145 is formed on the other sideof the second lead frame 14 facing the one side of the first lead frame12 to be inclined towards right and left sides of the second lead frame14. The first and second slant parts 125, 145 may have a linear orcurved shape.

A portion of the encapsulation material 20 is interposed between theopposite sides of the first and second lead frames 12, 14 facing eachother, and a force is applied to the interposed portion of theencapsulation material 20 and the opposite sides of the first and secondlead frames 12, 14. At this time, the slant parts 125, 145 disperse theforce diagonally, thereby preventing the encapsulation material 20 frombeing broken on the opposite sides of the lead frames 12, 14.Furthermore, since the slant part 125 of the first lead frame 12 has ashape surrounding the portion of the encapsulation material 20 adjacentthereto, it serves to more rigidly hold the encapsulation material 20.It should be noted that the breakage of the encapsulation material 20between the opposite sides of the lead frames 12, 14 may cause electricshorts or the like.

Additionally, a depressed part 126 is formed at the center of the oneside of the first lead frame 12 facing the other side of the second leadframe 14 to increase a separation between the first lead frame 12 andthe second lead frame 14. The depressed part 126 is located directlybelow a path of the bonding wire W which connects the first lead frame12 with the second lead frame 14. The depressed part 126 prevents thebonding wire W from being erroneously brought into contact with the leadframes 12, 14, and an electric short of the bonding wire W caused by theerroneous contact.

To fabricate the LED packages 1 as described above, a single metal sheetis processed to have a pattern of first and second lead frames 12, 14,followed by molding an encapsulation material 20 on the patterned metalsheet. Then, the lead frames 12, 14 are sawn per each encapsulationmaterial 20 supporting a pair of first and second lead frames 12, 14,thereby providing a plurality of LED packages 1. At this time, a processof removing burrs formed during sawing may be further included.

Although the present invention has been described with reference to theembodiments and the accompanying drawings, the present invention is notlimited to these embodiments and the drawings. It should be understoodthat various modifications, additions and substitutions can be made by aperson having ordinary knowledge in the art without departing from thescope and spirit of the invention, as defined only by the accompanyingclaims.

1. A light emitting diode (LED) package, comprising: a first lead frameand a second lead frame separated from each other; a chip mountingrecess formed in a first upper surface region of the first lead frame;an LED chip disposed on a bottom surface of the chip mounting recess andconnected to the second lead frame via a bonding wire; and a transparentencapsulation material arranged on the LED chip, wherein a thickness ofthe first lead frame in the first upper surface region is less than thethickness of the first lead frame in the other upper surface regions. 2.The LED package of claim 1, wherein the chip mounting recess comprisesan etched surface.
 3. The LED package of claim 1, further comprising: abonding recess formed in a first upper surface region of the second leadframe, wherein a thickness of the second lead frame in the first uppersurface region is less than the thickness of the second lead frame inthe other upper surface regions, and one end of the bonding wire isconnected with the second lead frame in the bonding recess.
 4. The LEDpackage of claim 3, wherein the bonding recess comprises an etchedsurface.
 5. The LED package of claim 1, further comprising: an openingor recess formed in at least one upper surface or lower surface of thefirst lead frame or second lead frame, wherein the transparentencapsulation material is arranged in the opening or recess.
 6. The LEDpackage of claim 1, wherein the LED chip is thinner than a depth of thechip mounting recess.
 7. The LED package of claim 1, wherein the firstlead frame and the second lead frame have opposite sides facing eachother, and the opposite sides each comprise a slanted part.
 8. The LEDpackage of claim 7, wherein at least one of the opposite sides comprisesa depressed part formed therein that widens a separation between thefirst lead frame and the second lead frame.
 9. The LED package of claim1, further comprising: a phosphor disposed in the transparentencapsulation material.
 10. The LED package of claim 1, furthercomprising: a resin part disposed in the chip mounting recess.
 11. TheLED package of claim 10, wherein the phosphor is disposed in the resinpart.
 12. The LED package of claim 9, wherein the phosphor is disposeddirectly on the LED chip.
 13. The LED package of claim 1, wherein thetransparent encapsulation material is formed by transfer molding. 14.The LED package of claim 1, further comprising: a plurality of scratchesformed on an upper surface or a lower surface of the first lead frame orthe second lead frame to increase a bonding force between the first leadframe or the second lead frame and the transparent encapsulationmaterial.
 15. The LED package of claim 7, wherein the first lead framecomprises a depressed part formed therein that widens a separationbetween the first lead frame and the second lead frame, and wherein thebonding wire is disposed directly above the depressed part.
 16. The LEDpackage of claim 10, wherein the phosphor is disposed in the transparentencapsulation material.